I do agree that the end of the last glacial period was the obvious immediate trigger for agriculture. But the “humans are the stupidest thing which could take off model” still holds, because evolution largely operates on a slower timescale than the glacial cycle.
Specifics: the last glacial period ran from roughly 115k years ago to 12k years ago. Whereas, if you look at a timeline of human evolution, most of the evolution from apes to humans happens on a timescale of 100k − 10M years. So it’s really only the very last little bit where an ice age was blocking takeoff. In particular, if human intelligence has been at evolutionary equilibrium for some time, then we should wonder why humanity didn’t take off 115k years ago, before the last ice age.
In particular, if human intelligence has been at evolutionary equilibrium for some time, then we should wonder why humanity didn’t take off 115k years ago, before the last ice age.
Yes we should wonder that. Specifically, we note
Humans and chimpanzees split about 7M years ago
The transition from archaic to anatomically modern humans was about 200k years ago
Humans didn’t substantially develop agriculture before the last ice age started 115k years ago (we’d expect to see archaeological evidence in the form of e.g. agricultural tools which we don’t see, while we do see stuff like stone axes)
Multiple isolated human populations independently developed agriculture starting about 12k years ago
From this we can conclude that either:
Pre-ice-age humans were on the cusp of being able to develop agriculture, and an extra 100k years of gradual evolution was sufficient to bump them over the relevant threshold
There was some notable period between 115k and 12k years ago where the rate of selective pressure on humans substantially strengthened or changed direction for some reason. Which might correspond to a very tight population bottleneck:
I do agree that the end of the last glacial period was the obvious immediate trigger for agriculture. But the “humans are the stupidest thing which could take off model” still holds, because evolution largely operates on a slower timescale than the glacial cycle.
Specifics: the last glacial period ran from roughly 115k years ago to 12k years ago. Whereas, if you look at a timeline of human evolution, most of the evolution from apes to humans happens on a timescale of 100k − 10M years. So it’s really only the very last little bit where an ice age was blocking takeoff. In particular, if human intelligence has been at evolutionary equilibrium for some time, then we should wonder why humanity didn’t take off 115k years ago, before the last ice age.
Yes we should wonder that. Specifically, we note
Humans and chimpanzees split about 7M years ago
The transition from archaic to anatomically modern humans was about 200k years ago
Humans didn’t substantially develop agriculture before the last ice age started 115k years ago (we’d expect to see archaeological evidence in the form of e.g. agricultural tools which we don’t see, while we do see stuff like stone axes)
Multiple isolated human populations independently developed agriculture starting about 12k years ago
From this we can conclude that either:
Pre-ice-age humans were on the cusp of being able to develop agriculture, and an extra 100k years of gradual evolution was sufficient to bump them over the relevant threshold
There was some notable period between 115k and 12k years ago where the rate of selective pressure on humans substantially strengthened or changed direction for some reason. Which might correspond to a very tight population bottleneck:
source: Robust and scalable inference of population history from hundreds of unphased whole-genomes
Note that “bigger brains” might also not have been the adaptation that enabled agriculture.